Temperature evolution of theGdmagnetization profile in strongly coupledGd∕Femultilayers

Abstract

The temperature evolution of the magnetization depth profile in $\mathrm{Gd}$ layers of a strongly coupled ${[\mathrm{Gd}(50\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})∕\mathrm{Fe}(15\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}})]}_{15}$ multilayer is studied using x-ray resonant magnetic scattering (XRMS) and x-ray magnetic circular dichroism (XMCD) techniques. XRMS yields a spatially resolved, element-specific, magnetization depth profile, while XMCD spatially averages over this profile. The combined data inequivocally show the presence of an inhomogeneous magnetic profile within the $\mathrm{Gd}$ layers at all measured temperatures between 20 and $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. These inhomogeneous profiles, which feature enhanced magnetic ordering near the $\mathrm{Gd}∕\mathrm{Fe}$ interface, were refined using both a kinematic Born approximation and a recently developed distorted-wave Born approximation, both of which include the contribution of structural and magnetic interfacial roughness. Calculations of the static magnetic configuration within a mean-field approach that neglects interfacial roughness are in agreement with the measured inhomogeneous profile and its temperature evolution. The results suggest that the enhanced $\mathrm{Gd}$ magnetization near the interface arises from its proximity to magnetically ordered $\mathrm{Fe}$.